Electric circuit breaker and indicating device therefor



T. CURZON Dec. 12, 1950 ELECTRIC CIRCUIT BREAKER AND INDICATING DEVICE THEREFOR Filed Feb. 4, 1948 2 Sheets-Sheet 1 Bl-METAL 6T9"? ELECTPOMAGNET.

x man/2'01 2 T C (/01 2 017/ Dec. 12, 1950 T. cuRzoN 2,534,107 ELECTRIC CIRCUIT BREAKER AND INDICATING DEVICE THEREFOR Filed Feb. 4, 1948 2 Sheets-Sheet2 Fig.2

Patented Dec. 12, 1950 ELECTRIC CIRCUITBREAKER AND INDICATING DEVICE THEREFOR Thomas Curzon, London, England, assignor to O. A. V. Limited, London, England Application February 4, 1948, Serial No. 6,304 In Great Britain December 8, 1944 3 Claims. 1

This invention relates to electric circuit breakers of the kind consisting at least in part of contacts which are operable automatically in response to some predetermined circuit condition. The object of the invention is to provide such a circuit breaker with a simple indicating device which can serve to give a visible indication that the automatic part of the breaker has performed its function and is also capable of testing the continuity of the circuit controlled by the breaker.

In the accompanying sheets of explanatory drawings:

Figure 1 is a diagram illustrating one mode of carrying the invention into efiect.

Figure 2 is a sectional side view of a circuit breaker embodying the invention, and Figure 3 is a side view taken at right angles to Figure 2 with the casing removed,

In carrying the invention into effect as illustrated in Figure 1, I employ four contacts a, b, c and d which are referred to herein as the first, second, third and fourth contact respectively. The first contact a is of resilient form and is adapted to be connected to one (e) of a pair of mutually co-operating contacts e, j in the circuit breaker, the latter contacts being separable by automatic means responsive to a predetermined circuit condition. The second contact b may be formed by a pair of lugs on a metal plate hereinafter described, and is adapted to be connected to the other breaker contact f. The third contact c is situated between the second and fourth contacts b, d, and may be formed by lateral projections on the ends of a yoke-like metal piece it extending between the lugs which form the second contact, this metal piece being embedded in a push button 1' made of transparent or translucent insulating material. The first contact a and the yoke-like piece h are adapted to be engaged by the caps at the opposite ends of a tubular signal lamp 7' having a filament interconnecting the caps, and the arrangement is such that the resilient pressure exerted by the first contact on the adjacent end of the lamp serves to hold the other end of the lamp in engagement with the yoke-like piece and to press the third contact against the second contact I). The fourth contact (1 may have the form of a ring against which the third contact c can be pressed by pushing the button i inwardly against the spring action of the first contact a. To detach the lamp 7' the button is rotated to a position in which the parts forming the third contact 0 can pass between the parts forming the second contact b. The button i, the third contact c, and

the lamp 7 can then be withdrawn from the other associated contacts. The fourth contact is adapted to be connected to the circuit containing the breaker contacts e, f at one side of a manually operable push-pull switch It in series with the breaker contacts, the connection between the first contact a and the breaker contact e being effected at the other side of the manually oper-' able switch. Also an electromagnet m (hereafter described) has its winding connected across the breaker contacts e, I.

As shown in Figure 1 the main electric circuit of the breaker contains the breaker contacts e, f, a bi-metal strip u carrying the contact I, and a pair of fixed contacts 2 forming parts of the manually operable switch It. Also this electric circuit comprises lines 20, 2| connecting one of a pair of current supply terminals :1: to one of the fixed contacts 2, lines 22, 23 connecting the other of the fixed contacts 2 to the breaker contact e, and lines 24, 25 connecting the bi-metal strip u to the other of the current supply termirials .1. Moreover, the first contact a is connected by a line 26 to the junction of the lines 22, 23, the second contact b is connected by a line 21 to the junction of the lines 24, 25, and the fourth contact 12 is connected by a line 28 to the junction of the lines 24, 25. Further, the winding of the electromagnet m is connected at one end to the line 24 and at the other end to the line 26. It will be understood that the bi-metal strip it serves in the usual manner to separate the breaker contacts e, ,f in response to a predetermined condition in the main electric circuit.

The arrangement is such that when the circuit controlled by the manually operable switch It and the automatically operated contacts e, f, of the circuit breaker are closed, the lamp 7' is short circuited by the latter contacts, but when these contacts are separated, the lamp is brought into action, its light being visible through the push button 1'. The lamp 9' then serves to give the desired indication that the circuit breaker is performing as desired. Should, however, no light be seen when the light is expected, this will indicate that a fault exists. This fault may be due to any one of several causes, namely, either the automatic part of the breaker has failed to act, or a discontinuity exists in some part of the circuit controlled by the breaker, or the lamp filament has become broken. To test the second possibility, the manually operable switch Ic is opened, and the push button 1' is pressed inwardly so as to bring the third and fourth contacts 0, d

' together. If the circuit controlled by the breaker is in order the lamp :1 will be lit. If no light is shown, this may be due to a break in the circuit or to a defect in the lamp The latter possibility can be tested by removing and inspecting the lamp. If the lamp and the circuit are found to be satisfactory, failure of the lamp to give the desired indication is then attributable to defective action of the automatically actuated contacts e, j of the breaker.

A preferred form of a circuit breaker embody ing the parts above described is shown in Figures 2 and 3. In this embodiment the electromagnet m is secured in any convenient manner to a supporting plate it having a central aperture, and is enclosed by a metal or other casing having an open end secured to the supporting plate, the other end of the casing being closed. The electromagnet m comprises a pair of metal frame members p, 11 a winding q, a core r, and a spring loaded armature s, the latter having one end hingedly attached to a metal plate t, and serving at its other end to carry the breaker contact 6. The plate t is carried by and electrically con-- nected to one end of the core T which at this end extends through but is insulated from the adjacent frame member p, the other end of the core being electrically connected to the other frame member p At a position adjacent to the armature 8 there is arranged within the casing o a bimetal strip it which at one end is secured to a lateral extension 1) on another metal plate 10, the latter being mounted on but insulated from the end of the core 1' carrying the first mentioned plate 13. The other end of the bi-rnetal strip u serves to carry the other breaker contact f. The ends of the electromagnet winding q are electrically c-onected to the two metal plates t, w respectively. Also the plate w and the frame member p carry terminal screws x for connection to the circuit to be controlled, these screws being arranged to extend through an aperture 1 in the closed end of the casing o.

For electrically interconnecting the frame members p, p I employ the manually operable switch 7c above mentioned. This switch is of the push-pull type and has a pair of fixed contacts 2 and a pair of complementary movable contacts 3. The fixed contacts 2 are respectively secured to adjacent parts of the frame members 12, p and are formed with V-shaped parts for accommodating complementary parts of the movable contacts 3. The latter are interconected by or formed integrally with a resilient metal bridge piece 4, and are operable by an axially movable stem 5 which passes through the central aperture in the supporting plate 12 and is provided at its outer end with a finger piece 6 made from insulating material. The finger piece 6 is formed with a tubular extension 6 which is slidable in a fixed guide I on the supporting plate 11.. The stem 5 passes through a central hole in the bridge piece 4 and is surrounded by a pair of helical compression springs 8 through which movement can be imparted by the stem to the bridge piece for actuating the movable contacts 3, one of the springs being situated between the bridge piece and the finger piece 6, and the other being situated between the bridge piece and a head 9 on the inner end of the stern. Secured to the parts of the frame members p, p which carry the fixed contacts 2 are a pair of insulating pieces III which at their adjacent sides are formed with V-shaped recesses II for accommodating the movable contacts 3.

Y When the switch is is closed its movable contacts 3 engage the fixed contacts 2. To open this switch a push is exerted on the finger piece 6. The effect of this is to compress the spring 8 arranged between the bridge piece 4 and the finger piece 6 until this spring causes the movable contacts 3 to be disengaged from the fixed contacts 2 and moved into engagement with the recesses H in the insulating pieces 10. Reclosure of the switch is is effected by exerting a pull on the finger piece 6. This causes the other spring 8 to be compressed until it causes the movable contacts 3 to be disengaged from the recesses II and re-engaged with the fixed contacts 2. It will be seen therefore that both the opening and closing movements of the contacts 3 are effected rapidly under spring action.

The breaker contacts e, f are normally closed, and when in this condition they short-circuit the electromagnet winding q which is of relatively high resistance. Assuming that the push-pull switch It is closed and that the terminal screws .1: are connected to the circuit to be controlled, the contacts e, f remain closed so long as normal conditions exist in the said circuit, but in the event of a short-circuit or other overload condition causing abnormal heating of the bi-metal strip u the contacts e, f are separated, whereupon current flows through the winding q and excites the electromagnet m. This causes rapid and complete separation of the contacts e, j and prevents reclosure thereof in consequence of the strip u cooling. When removing the fault the push-pull switch is is opened. The electromagnet m then ceases to act, and the cooled strip u allows the contacts e, f to come together again.

At the outer side of the frame member 1) of the electromagnet m the casing 0 serves as a housing for the above mentioned two-way switch formed by the contacts a, b, c and d, and the adjacent part of the supporting plate n is formed with a hole l2 through which extends the push button i associated with the yoke-like piece 11. The first contact a is carried by and electrically connected to the electr-omagnet core 1*. The lugs forming the second contact I) are provided on the metal plate 10 and are situated above the first contact a, whilst the lateral projections provided on the yoke-like piece h and forming the third contact c are situated at the underside of the said lugs, the upper sides of the latter being recessed to accommodate the said projections. Further the fourth contact d is situated around the tubular signal lamp 7' at a position between the first and third contacts a, c, and is secured to the adjacent frame member 12 of the electromagnet m. The two-Way switch and the signal lamp function in the manner previously described.

It will be understood that the various parts of the example shown in Figures 2 and 3 are electrically connected in the manner shown diagrammatically in Figure 1. To make this clear the lines 20 to 28 of Figure 1 will now be traced in Figure 2. The lines 20, 2| are formed by the frame member 1). The lines 22, 23 are formed by the frame member 11 the core r, the plate t, and the armature s. The lines 24, 25 are formed by the plate w and its extension 1;. The line 26 is formed by the end of the core 1" remote from the plate p The line 21 is formed by the member on which the lugs forming the second contact b are provided, and which is connected to the plate 10. The line 28 is formed by the member on which the fourth contact at is provided, and which is connected to the frame member p.

The winding q of the electromagnet m is connected at one end to the core 1 and at the other end to the plate '10.

By this invention I am able to provide the desired indicating means for use with certain forms of circuit breakers in a very simple and convenient form. The invention is not, however, restricted to the example described as constructional details may be modified to suit different requirements.

Having thu described my invention what I claim as new and desire to secure by Letters Patent is: I

1. An electric circuit breaker comprising in combination a main electric circuit including a pair of norm-ally closed main complementary contacts, means for separating said contacts in response to an overload condition in said circuit, a control switch arranged in series with said contacts, an electric signal. lamp, and a manually operable two-way switch having fixed and mov able contacts which in one position of said twoway switch connect said signal lamp across said main complementary contacts to enable said lamp to give a visible indication when said main comcomplementary contacts, a third contact between a? which and said resilient contact said signal lamp is arranged, and which is normally held against said second contact by said signal lamp under pressure exerted by said resilient contact, a push button made from light-transmitting material and secured to said third contact, and a fourth contact against which said third contact can be pressed by said push button in opposition to the pressure exerted on said signal lamp by said resilient contact, said fourth contact being connected to said main electric circuit at the side of said control switch remote from said main complementary contacts.

3. An electric circuit breaker as claimed in claim 1, in which said two-way switch comprises in combination a resilient contact connected to one of said main complementary contacts, a second contact connected to the other of said main complementary contacts, a third contact between which and said resilient contact said signal lamp is arranged, and which is normally held against said second contact by said signal lamp under pressure exerted by said resilient contact, a push button made from light-transmitting material and secured to said third contact, and a fourth contact against which said third contact can be pressed by said push button in opposition to the pressure exerted on said signal lamp by said 1'e-- silient contact, said fourth contact being connected to said main electric circuit at the side of said control switch remote from said main complementary contacts, and said third contact being disengageable by angular movement of said push button from said second contact to enable said signal lamp to be removed for inspection.

THOMAS CURZON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 7 Date 

